1
Std 8Mental Maths Competition® 2013
Topics Included.
(1) Q. No. 1 to 50 are based on basic. Calculation questions related to Addition,
Subtraction, Multiplication and Division, doubling and halving.
(2) Student should know multiplication tables from 2 to 30.
(3) Number pattern. Doubling & Halving.
(4) Mixed operations (BODMAS), Decimal Fraction, Fractions, time
(5) L.C.M & H.C.F., divisibility of 2, 3, 4, 5, 6, 8, 9, 10, 11
(6) Integers (Add, Subtract, Multiply, Divide) Mixed sums
(7) Find day and date in a given calender year.
(8) Calculation of percentage, Average, Ratio, simple equation, discount, profit &
Loss percentage.
(9) Square and Square root from 1 to 30, Cubing a number from 1 to 15
(10) Conversions: kg hecto grm, deca gram, gram, decigram, centigram, miligram
km hecto metre, deca mt, metre, deci mt, centi mt, mili mt.
kl hecto litre, deca lt, litre, deci lt, centi lt, mili lt.
(11) Area and perimeter of square and rectangle. Angles of a triangle.
Instructions for the Competition
1. Time : 1½hr2. Students can use HB Pencil for marking answers in OMR sheet.3. Result of the Competition will be declared on 28th November, 2013.4. The application of rechecking of marks should be made within 10 days of
declaration of results along with rechecking fees ̀ 100 in cheque only.
5. Every participant scoring more than 35% will be given certificate ofparticipation.
6. Winners [ Rank 1 to Rank 3] from each std will be felicitated withTrophies in a specially arranged Award Function.
7. Medals for consolation prize winners [Rank 4th to Rank 10th] willbe sent by courier at their residence along with the certificate.
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Std 8Mental Maths Competition® 2013
SECTION 1 (Mental Maths Calculation)
1. (38 × 12) + (38 × 48) = _____(a) 2180 (b) 2280
(c) 2270 (d) 2260
2. (95 × 36) – (16 × 95) = _____(a) 1700 (b) 1900
(c) 1850 (d) 1670
3. (12 × 37) + (6 × 9) + (18 × 17)=_____(a) 714 (b) 624
(c) 804 (d) 914
4. (65 × 3) + (81 × 4) – (36 × 5)=_____(a) 719 (b) 829
(c) 339 (d) 429
5. (81 × 5) – (36 × 5) + (13 × 9)=_____(a) 342 (b) 442
(c) 312 (d) 412
6. (25% of 164) + (50% of 198) =_____(a) 135 (b) 130
(c) 150 (d) 140
7. (50% of 168) – (25% of 136)=_____(a) 30 (b) 40
(c) 50 (d) 60
8. (50% of 172) + (25% of 120)–(20% of 150 ) = _____(a) 76 (b) 86
(c) 84 (d) 96
9. (half of 280) + (one thirdof 120) = _____(a) 160 (b) 180
(c) 170 (d) 190
10. (one third of 360) – (half of126) = _____(a) 47 (b) 37
(c) 57 (d) 42
11. square of 36 + square 14 =_____(a) 2028 (b) 1792
(c) 1592 (d) 1492
12. square of 85 – square 35 =_____(a) 4000 (b) 3000
(c) 5000 (d) 6000
13. square of 30 + square of 20– square of 15 = _____(a) 1075 (b) 1065
(c) 1005 (d) 1035
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Std 8Mental Maths Competition® 2013
14. square of 18 – square root of625 = _____(a) 399 (b) 299
(c) 199 (d) 499
15. square of 39 + cube root of343 = _____(a) 1258 (b) 1528
(c) 1529 (d) 1520
16. square root of 144 + cubeof 8 = _____(a) 624 (b) 524
(c) 512 (d) 634
17. cube of 5 + square root1225 =(a) 130 (b) 140
(c) 160 (d) 180
18. Sum of all the divisor of 45= _____(a) 60 (b) 78
(c) 70 (d) 40
19. Sum of all the divisor of 30(a) 32 (b) 82
(c) 72 (d) 92
20. Sum of all prime divisors of2310(a) 18 (b) 38
(c) 48 (d) 28
21. Select the greatest numberfrom the given operations.(a) 98 × 3 (b) 398 – 146
(c) 98 + 126 (d) 23 × 16
22. Select the smallest numberfrom the given operations.(a) 36 × 2 (b) 123 – 45
(c) 108 ÷ 3 (d) 5 × 12
23. If 335 is divided by 25, theremainder is ______(a) 5 (b) 6
(c) 9 (d) 10
24. If 968 is divided by 12, theremainder is ______(a) 11 (b) 3
(c) 8 (d) 13
25. If 1098 is divided by 32, theremainder is ______(a) 10 (b) 20
(c) 30 (d) 15
26. If 1225 is divided by 21, theremainder is ______(a) 0 (b) 2
(c) 3 (d) 7
27. 9213 × 21 = ______(a) 193473 (b) 193483
(c) 193493 (d) 0
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Std 8Mental Maths Competition® 2013
28. 1098 × 45 = ______(a) 49401 (b) 49410
(c) 49510 (d) 49520
29. 3.95 × 1.2 = ______(a) 4.68 (b) 4.98
(c) 4.74 (d) 4.12
30. 5.15 × 2.4 = ______(a) 13.36 (b) 12.36
(c) 14.36 (d) 0.36
31. H.C.F. of 36, 72, 96 is ______(a) 13 (b) 14
(c) 12 (d) 15
32. L.C.M. of 45, 36 and 72 is______(a) 360 (b) 320
(c) 180 (d) 350
33. 4 – 3.009 = ______(a) 0.961 (b) 0.993
(c) 0.019 (d) 0.991
34. 15.85 + 36.92 – 12.21 = ____(a) 41.56 (b) 32.96
(c) 40.56 (d) 90.56
35. 5 41
+ 651
=
(a) 11 203
(b) 11 209
(c) 11 213
(d) 0 200
36. – 1 31
= 65
(a) 2 61
(b) 3 51
(c) 3 51
(d) 4 61
37. (1.36 × 2.9) + (7.1 × 1.36) =______(a) 13.06 (b) 13.60
(c) 13.006 (d) 13.0
38. Double of 3045 = ______(a) 6010 (b) 6070
(c) 6090 (d) 6020
39. Half of 3098 = ______(a) 1649 (b) 1549
(c) 1643 (d) 1540
40. The ratio of 45 min to45 hour is ______(a) 1:16 (b) 1:30
(c) 1:60 (d) 1:10
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Std 8Mental Maths Competition® 2013
41. 160 × 10 ÷ (5 × 4 )= ______(a) 40 (b) 100
(c) 60 (d) 80
42. 94 – (31 – 103) = ______(a) –22 (b) – 166
(c) 166 (d) 22
43. – 2 + = – 9
(a) 7 (b) – 7
(c) 11 (d) – 11
44. (203 – 318) ÷ 23 = ______(a) – 5 (b) – 6
(c) – 7 (d) 5
45. (15) × (2) + (– 4) × (5) ÷ (–5)(a) 34 (b) – 4
(c) 2 (d) – 2
46. 360288
=
(a) 54
(b) 56
(c) 45
(d) 76
47. Find nineth term in the givenseries.25, 36, 49, 64, ___, ___, ___(a) 169 (b) 196
(c) 144 (d) 121
48. 54
÷ 256
× 158
=
(a) 169
(b) 916
(c) 34
(d) 43
49. 9 × 38 + 9 × 12 = ______
(a) 350 (b) 450
(c) 400 (d) 500
50. 125 × 10 + 125 × 90 = ______(a) 1150 (b) 12500
(c) 13500 (d) 14500
51. 10.35 ÷ 1.5 = ______(a) 6.5 (b) 6.7
(c) 6.9 (d) 6.4
52. 759 ÷ 1.1 = ______(a) 660 (b) 690
(c) 630 (d) 670
53. 35:70 = 7: ______
(a) 9 (b) 8
(c) 7 (d) 14
54. If 3 bags of Soyabeen seedscost ` 2250. Find the cost of7 such bags.(a) 5200 (b) 5250
(c) 5300 (d) 5270
SECTION 2(Mental Maths Concepts)
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Std 8Mental Maths Competition® 2013
55. The perimeter of triangle is55 cm, if one of its side is15 cm. If the other two sideare equal find their lengths.(a) 25 cm (b) 20 cm
(c) 30 cm (d) 28 cm
56. 3y2
= 158
then y =
(a) 0.8 (b) 0.4
(c) 0.9 (d) 0.5
57. The ratio of 1 meter: 60 cm is______(a) 5:4 (b) 5:3
(c) 3:5 (d) 3:4
58. The ratio of ` 2:75 paise =______(a) 8:3 (b) 3:8
(c) 5:3 (d) 3:5
59. 3t = 7t – 12, t = ______
(a) 0 (b) 1
(c) 2 (d) 3
60. Find the number whose 5%is 25.(a) 50 (b) 500
(c) 1500 (d) 400
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Std 8Mental Maths Competition® 2013
SECTION 3 (Mental Maths Challenge)
61. Raj purchased following items from the supermarket 10 kg atta at`15 per kg; 2 kg dal moong at ` 32.50 per kg, 1 kg dal Udad at` 43.50 per kg and 1 kg sugar at ` 14.50 per kg. How much didhe pay to the cashier, if the cashier gave him ` 27 back?(a) ` 165 (b) ̀ 235 (c) ̀ 273 (d) ̀ 300
62. Find the smallest number which on being divided by 20, 40, 60and 75 leaves 18 as remainder.(a) 5 (b) 23 (c) 600 (d) 618
63. Find the radius of a circle whose circumference is 13.2 cm.(a) 1.4 cm (b) 2.1 cm (c) 4.2 cm (d) 5.6 cm
64. A car travels 579.6 km in 9 hours. Find the distance covered in5 hours.(a) 64.40 km (b) 115.92 km (c) 322 km (d) 1043.28 km
65. If a library there were 5000 books. Out of this 675 books werediscarded what percentage was discarded?(a) 8.5% (b) 10% (c) 13.5% (d) 15%
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Std 8Mental Maths Competition® 2013
66. Sunil bought an old motor cycle for `15000 and spent ̀ 3000 forits repairs. For how much shall be sale it to earn profit of 10%?(a) ̀ 16500 (b) ̀ 18000 (c) ̀ 19800 (d) ̀ 17500
67. To make 67 dresses 368.5 m of cloth was used. To make 75dresses how much of the cloth will be required?(a) 412.5 m (b) 411.5 m (c) 390 m (d) 395 m
68. 3[15.2 + {(6.5 + 24.5) × 2 + (7.8 – 2.3)}] =(a) 155.1 (b) 248.1 (c) 310.2 (d) 333.1
69. In a hostel the consumption of wheat by 180 students in 9 monthis 3600 kg. Find the wheat required for 85 student in the sameperiod.(a) 1300 kg (b) 1500 kg (c) 1700 kg (d) 1900 kg
70. The ratio of income to expenditure of Mr. Kiran is 9 : 8.Find his saving if his income is ̀ 18000.(a) ̀ 1500 (b) ̀ 2000 (c) ̀ 2500 (d) ̀ 3000
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Std 8Mental Maths Competition® 2013
71. Calculate the number of years, months and days between7-8-1992 and 3-5-2006.(a) 14Y-3M-4D (b) 14Y-8M-27D (c) 13Y-3M-4D (d) 13 Y-8M-27D
72. If x= 2, y = 1, z = 4 and a = 5, find the value of
zxy
– axy
(a) 53
(b) 103
(c) 51
(d) 101
73. Divide 0.0042 by 125.(a) 0.0336 (b) 0.00336 (c) 0.000336 (d) 0.0000336
74. The square plot has a side 80 m long. Find the cost of levellingif at ` 6.50 per sq.metre.(a) ̀ 0.4160 (b) ̀ 41.60 (c) ̀ 41600 (d) ̀ 4160
75. Simplify : 9.6 ÷ 12 + 0.32 × 10 – 1.1 = ________(a) 2.77 (b) 2.9 (c) 3.5 (d) 5.1
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Std 8Mental Maths Competition® 2013
1. Ram, Ravina, Suresh and Srushti are respectively 12 yrs 3 months,13 years 9 months, 13 year 7 months and 12 years 5 monthsold. Find their average age.(a) 12 yrs 6 months (b) 12 yrs 11 months
(c) 13 yrs 1 month (d) 13 yrs 3 months
2. The H.C.F and L.C.M. of two number are 9 and 180 respectively.If one of the number is 36, find the other one.(a) 40 (b) 45 (c) 50 (d) 180
3. Andy borrows a sum of ̀ 3600 from Richa at the rate of 8% p.a.After 1 year 8 months, how much simple interest will he have topay?(a) ` 288 (b) ̀ 480 (c) ` 518 (d) ̀ 648
4. There are 4800 books in a library. If 12.5% new books werepurchased and 400 old books were discarded, how many bookswere left in the library?(a) 600 (b) 4400 (c) 5000 (d) 5400
5. Simplify: - 253850901 – 189872925 + 7523563(a) 71401539 (b) 71491539 (c) 71501539 (d) 71501439
(Extra practise question)
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Std 8Mental Maths Competition® 2013
6. A student has to secure 35% of the maximum marks to pass.He secures 280 marks and fails by 175 marks. Find the maximummarks.(a) 500 (b) 800 (c) 1050 (d) 1300
7. 5 21
–
431
87
65of
52of
52
(a) 4 31
(b) 4 32
(c) 5 61
(d) 5 32
8. Manan repaid ` 5500 in 8 months which he had borrowed at13.5% per annum. How much simple interest did he pay.(a) ̀ 247.50 (b) ̀ 371.25 (c) ̀ 495 (d) ̀ 742.50
9. Find the difference of the greatest and least numbers of five digitsby formed by using 0, 1, 2, 3 and 4 once only.(a) 30870 (b) 30906 (c) 31176 (d) 32976
10. What is the 6th term of the sequence shown?80, 40, 20, ..........
(a) 1 (b) 5 (c) 141
(d) 2 21
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Std 8Mental Maths Competition® 2013
11. A square & a rectangular plot of land have same perimeter. If thesquare is of side 60 cm & rectangle is of length 70 cm, then thearea of the rectangle is(a) 3500 cm² (b) 2800 cm² (c) 2500 cm² (d) 2200 cm²
12. A boy is 25 yrs younger than his father. Three years ago, the boy’sage was one-sixth of the age of his father, then present age of boyis(a) 10 yrs (b) 6 yrs (c) 8 yrs (d) 4 yrs
13. In a two digit number, the unit place digit is 2. If the digits are
interchanged, the new number formed is 83
times the old
number. What is the number?(a) 36 (b) 62 (c) 72 (d) 52
14. The speed of car is 54 21
km per hour. What is the distance
travelled in 27
hours & 235
minutes?
(a) 484929
km (b) 489972
km (c) 489919
km (d) 242479
km
15. A reduction of 20% in the price of sugar enables Mrs. Lal to buyan extra 5 kg of it for ` 320. What is the reduced price per kg?(a) `12.80 per kg (b) ̀ 14.60 per kg (c) ` 16 per kg (d) ̀ 16.90 per kg
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Std 8Mental Maths Competition® 2013
16. This year, your brother Pratham will be 2yrs from being twice asold as your sister Jeet. The sum of Pratham’s age & three timesJeet’s age is 68. How old is Jeet?(a) 12 yrs (b) 14 yrs (c) 13 yrs (d) 15 yrs
17. Which of the following expression is correct?(a) 7 ÷ 7 + 7 × 7 = 50 (b) 7 + 7 ÷ 7 × 7 = 50
(c) 7 × 7 ÷ 7 + 7 = 50 (d) 7 – 7 × 7 + 7 = 50
18. A swimming pool is 30 m long & 15 wide. How many Kilolitres ofwater must be pumped into it so as to raise the level of water by4.5 m?(a) 2.025 kl (b) 20.25 kl (c) 202.5 kl (d) 2025 kl
19. If 96.5% of the students are present in the school & number ofabsent students is 42, find the total number of students in theschool.(a) 1050 (b) 1200 (c) 1680 (d) 4053
20. The cost of a wall clock is ` 360. Find the selling price if the gainis 15%.(a) ` 54 (b) ̀ 306 (c) ̀ 414 (d) ̀ 423.50
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Std 8Mental Maths Competition® 2013
21. Simplify:-
431
87
65of
52
215
(a) 4 31
(b) 4 32
(c) 5 31
(d) 5 32
22. In an office 10 clerks get a salary of ` 2400 each & 4 officers get asalary of ` 4500 each. Find the average salary of the employee inthe office.(a) ̀ 2400 (b) ̀ 3000 (c) ̀ 4500 (d) ̀ 6900
23. If two complementary angles are in the ratio 4:5. Find the smallerone.(a) 400 (b) 500 (c) 800 (d) 1000
24. The perimeter of a rectangular field is 240 m. If the length is85 m, find its area.(a) 2695 sqm (b) 2795 sqm (c) 2975 sqm (d) 29.75 sqm
25. There were only two candidates in an election. One got 62% voteselected by a margin of 144 votes. The total number votes were(a) 500 (b) 600 (c) 700 (d) 800
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Std 8Mental Maths Competition® 2013
Answer Sheet
1 b 2 6 d 5 1 c
2 b 2 7 a 5 2 b
3 c 2 8 b 5 3 d
4 c 2 9 c 5 4 b
5 a 3 0 b 5 5 b
6 d 3 1 c 5 6 a
7 c 3 2 a 5 7 b
8 b 3 3 d 5 8 a
9 b 3 4 c 5 9 d
1 0 c 3 5 b 6 0 b
1 1 d 3 6 a 6 1 d
1 2 d 3 7 b 6 2 d
1 3 a 3 8 c 6 3 b
1 4 b 3 9 b 6 4 c
1 5 b 4 0 c 6 5 c
1 6 b 4 1 d 6 6 c
1 7 c 4 2 d 6 7 a
1 8 b 4 3 b 6 8 b
1 9 c 4 4 a 6 9 c
2 0 d 4 5 a 7 0 b
2 1 d 4 6 a 7 1 d
2 2 c 4 7 a 7 2 d
2 3 d 4 8 b 7 3 d
2 4 c 4 9 b 7 4 c
2 5 a 5 0 b 7 5 b
1 c 9 d 17 a2 b 10 d 18 d3 b 11 a 19 b4 c 12 c 20 c5 c 13 c 21 b6 d 14 c 22 b7 c 15 a 23 a8 c 16 b 24 c
25 b
Answers for extra practice questions
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Std 8Mental Maths Competition® 2013
Section 3 (Solution)61) Atta 10 × 15 = 150
Moong dal 2 × 32.5 = 65Udad dal 1 × 43.5 = 43.5Sugar 1 × 14.5 = 14.5Total 273He paid to cashier = 273 + 27
= ` 300
62) L.C.M. of 20, 40, 60 and 75 is 600.Hence required number = 600 + 18
= 618
63) Circumference = 2r
13.2 = 2 × 722
× r
r = 22272.13
r = 2.1 cm
64) Speed = timedistance
= 9579.6
= 64.4 km/hrdistance covered in 5 hrs. = 64.4 × 5
= 322 km
65) % of books discarded
= 5000675
× 100
= 13.5%
66) Total cost = 15000 + 3000= 18000
cost price selling price100 11018000 x
x = 10011018000
= 19800
67) Cloth required for 1 dress
= 675.368
= 5.5 m Amt of cloth required
= 75 × 5.5m = 412.5m.
68) 3 [15.2 + {(16.5 + 24.5) × 2 + (7.8 – 2.3)}]= 3 [15.2 + {31 × 2 + 5.5}]= 3 [15.2 + {62 + 5.5}]= 3 [15.2 + 67.5]= 3 [82.7]= 248.1
69) Students Months Wheat 180 9 3600 85 9 xSince No. of months is same,
x = 180360085
= 1700
70) Income : expenses = 9 : 8 Income : savings = 9 : 1
Income savings 9 118000 x
x = 9118000
= 2000
71) From 7 – 8 – 1992 till 7 – 8 – 2005 is 13 years.Then till 7 – 4 – 2006 is 8 monthsThen till 3 – 5 – 2006 is 27 days.
72) zxy
– axy
= 4)1()2( – 5
)1()2(
= 21
– 52
= 1045
= 101
73) 1250042.0
= 0.0000336
74) Area of square = (80)²= 6400 m²
cost of levelling = 6400 × 6.50= 41600
75) 9.6 ÷ 12 + 0.32 × 10 – 1.1= 0.8 + 3.2 – 1.1= 4 – 1.1= 2.9
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Std 8Mental Maths Competition® 2013
Extra Practice Questions (Solution)
1) Average age = 4ageTotal
= 4)149163165147(
months
= 4624
= 156 months= 13 years.
2) L.C.M × H.C.F = Product of two numbers9 × 180 = 36 × x
x = 361809
x = 45
3) P = 3600, R = 8%, T = 1 yr 8 months = 321 yrs.
SI = 100RTP
=100
83213600
= 480
4) No. of books = 4800
New books = 1005.12
× 4800 = 600
discarded old books = 400No. of books left = 4800 + 600 – 400
= 5000
5) 253850901+ 2523563 261, 374, 464– 189, 872, 925
71, 501, 539
6) Passing marks = 280 + 175= 455
max. marks passing marks100 35 x 455
x = 35100455
= 1300
7) 5 21
–
43
187
65
of52
of52
= 211
–
47
87
31
of52
= 211
–
74
87
31
of52
= 211
–
21
31of
52
= 211
–
6
32of
52
= 211
–
65of
52
= 211
– 31
= 6233
= 631
= 5 61
8) P = 5500
T = 8 months = 32
yr.
R = 13.5% p.a.
SI = 100RTP
=100
5.13325500
= 495
9) Greatest number = 43, 210least number = 10, 234
difference = 32, 976
10) 80 40 20 10 5 25
÷ 2 ÷ 2
25
= 212
11) Perimeter of square = Perimeter of rectangle4(60) = 2(70 + x)240 = 140 + 2x2 x = 100x = 50
Area of rectangle = 50 × 70= 3500 cm²
12) Present age of boy = xPresent age of father = x + 253 yrs ago,
age of boy = x – 3age of father = x + 25 – 3
= x + 22
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Std 8Mental Maths Competition® 2013
x – 3 = 61
(x + 22)
6(x – 3) = x + 226x – 18 = x + 226x – x = 22 + 185 x = 40
x = 8
13) Let the ten’s digit = x Number = 10x + 2 Number obtained by interchanging the digits
= 20 + x
20 + x = 83
(10x + 2)
160 + 8x = 30x + 6160 – 6 = 30x – 8x
154 = 22xx = 7
The required number = 72
14) 27
hrs and 235
minutes
=
601
235
27
hrs
= 27
+ 247
hrs.
= 2491
hrs.
distance = speed × time
= 54 21
× 2491
= 2109
× 2491
= 489919
km
15) Let the originalprice = ` x per kg
New price = x + 10020
× x
= x – 5x
= 5x4
Original quantity = x320
New quantity = 5/x4320
= x45320
= x400
x400
– x320
= 5
x80
= 5
x = 580
x = 16 Original price = ` 16
reduced price = 16 – 10020
× 16
= 12.80 per kg
16) Present age of Jeet = x yrs.Pratham’s age = 2x – 2
3x + 2x – 2 = 685 x = 70x = 14
17) Option (a) is correct7 ÷ 7 + 7 × 7= 1 + 7 × 7= 1 + 49= 50
18) Volume = 30 × 15 × 4.5= 2025 m³= (2025 × 100 × 100 × 100)cm³
=
1000
1001001002025l
= (2025 × 1000)l
=
1000
10002025kl
= 2025 kl
19) Present students = 96.5% Absent students = 100 – 96.5
= 3.5%
1005.3
× x = 42
x = 5.310042
x = 1200
20) C.P S.P100 115360 x
x = 100115360
= 414
21) 5 21
–
431
87
65of
52
= 211
–
47
87
65
of52
19
Std 8Mental Maths Competition® 2013
= 211
–
74
87
65
of52
= 211
–
21
65of
52
= 211
–
21
31
= 211
– 632
= 211
– 65
= 6533
= 628
= 314
= 324
22) Total salary = 10 × 2400 + 4 × 4500= 24000 + 18000= 42000
Average salary = 1442000
= 3000
23) Smaller angle = 544 × 90
= 94
× 90
= 40°
24) P = 2 (l + b)240 = 2 (85 + b)120 = 85 + bb = 35
Area = l × b= 85 × 35= 2975 m²
25) Winner 62%Looser 100 – 62 = 38%Margin = 62 – 38
= 24%
10024
× x = 144
x = 24100144
x = 600.